In a conventionally known linear motion guide unit, retainer means for retaining cylindrical rollers is snap-on fixed to a slider to thereby increase the rated load of the slider. In the linear motion guide unit, a retainer plate is disposed between the cylindrical rollers disposed along an upper raceway surface of a carriage and the cylindrical rollers disposed along a lower raceway surface of the carriage. A holder portion of a fixing band is engaged with an engagement groove of the retainer plate and with engagement grooves of end caps. Engagement beaks at the ends of bend portions of the fixing band are engaged with respective engagement holes formed in the end caps. The retainer means for retaining the cylindrical rollers is incorporated in the slider and retains the cylindrical rollers to a load-carrying race formed by a guide rail and the carriage (see, for example, Japanese Patent Application Laid-Open No. H07-91446).
In another conventionally known linear motion guide unit, a retainer plate has a light structure and can be simply and easily held to end caps to thereby reduce the size of a slider. The linear motion guide unit is composed of a guide rail, and the slider moving on the guide rail via rollers. The slider has a carriage and end caps fixed to the respective opposite ends of the carriage. The rollers located on the raceway surface side of the carriage are retained to the carriage by the retainer plate. The retainer plate is fixed to the carriage by screwing fastening bolts inserted through respective insertion holes formed in the carriage into respective nuts disposed at the back of the retainer plate. The retainer plate is composed of a pair of flat plate portions formed by bending a thin plate along its longitudinal direction in such a manner as to have a V-shaped cross section. The pair of flat plate portions are formed to be greater in length than the carriage, and opposite end portions thereof are fixedly fitted into respective engagement grooves formed in the end caps. The flat plate portions guide the end surfaces of the rollers rolling on the upper and lower raceway surfaces of the carriage to thereby retain the rollers on the raceway surfaces. In order to hold the retainer plate to the slider, the carriage has the insertion holes formed therein, and the bolts are screwed into the respective nuts provided on the back of the retainer plate (see, for example, Japanese Patent Application Laid-Open No. 2014-234858 (FIG. 28)).
Meanwhile, a conventional large-sized roller-type linear motion guide unit has in some cases involved the following problem: in the case of fixing a retainer plate made of resin to a carriage by tightening fastening bolts with strong tightening torque, tightening forces (axial forces) of the bolts are applied directly to the retainer plate and cause deformation of the guide surfaces; as a result, for example, the guide surfaces swell to thereby narrow load-carrying races between a guide rail and the carriage, resulting in a failure to attain smooth circulation of rollers. Thus, there has been desired a structure free from deformation of the guide surfaces of the retainer plate even in attaching the retainer plate to the carriage by screwing the fastening bolts into the retainer plate.
For example, the linear motion guide unit shown in FIG. 15 and FIGS. 16(a) to 16(c) is a large-sized roller-type mass-produced product in which a retainer plate 7 is composed of a retainer member 12 made of resin and a fixing member 13 disposed on the back side of the retainer member 12 and formed of a long and narrow metal plate having the same length as that of the retainer member 12. The retainer member 12 has a recess 50 in which the fixing member 13 is disposed, and through holes 53 through which fastening bolts 41 are inserted. The fastening bolts 41 are screwed into respective female threads 42 provided in the fixing member 13 to thereby fix the retainer plate 7 to a carriage 3. However, since the retainer member 12 of the retainer plate 7 is held between the carriage 3 and the fixing member 13, tightening forces (axial forces) of the fastening bolts 41 are applied to the retainer member 12. Accordingly, if the fixing member 13 is fixed to the carriage 3 with strong tightening torque, guide surfaces 32 of the retainer member 12 swell or distort at a bolt position, resulting in a reduction of the dimension between the guide surfaces 32 of a load-carrying race. As a result, the amount of interference between the guide surface 32 and a roller end surface 25 increases; consequently, a roller 5 fails to smoothly pass, and sliding resistance increases. In the large-sized linear motion guide unit shown in Japanese Patent Application Laid-Open No. H07-91446 whose applicant is the same as the applicant of the present invention, the retainer plate made of resin is fixed to the carriage with the fixing band made of a metal. If the fixing band excessively presses the retainer plate toward the carriage, the following problem may arise: the retainer plate is deformed to thereby reduce the dimension between the guide surfaces of the load-carrying race; as a result, the guide surface of the retainer plate and the end surface of a roller interfere with each other; accordingly, the roller fails to smoothly pass, and sliding resistance increases. In the linear motion guide unit described in Japanese Patent Application Laid-Open No. 2014-234858 whose applicant is the same as the applicant of the present invention, the retainer plate is fixed to the carriage by screwing the bolts inserted through respective through holes formed in the carriage, into respective nuts disposed in a recess formed in the back of the retainer plate. Accordingly, a similar problem may arise as in the case of the above-mentioned large-sized roller-type linear motion guide unit.